Apparatus and method for applying a fluid to a component

ABSTRACT

Apparatus for applying a fluid to a target area of a component is provided, the apparatus comprising a fluid applicator  10  and means  12, 300, 400  for guiding the fluid applicator  10  along a predetermined path with respect to the component  26 ; the fluid applicator  10  comprising a body  14  and an application head  50, 100, 200  mounted on the body  14  and operable in use to be brought into physical contact with the component  26.

The present invention relates to an apparatus and method for applying afluid to a component. The invention is particularly but not exclusivelyrelated to an apparatus and method for applying a chemical etchant to atarget area of a component.

Chemical etching is a commonly used technique for removing one or moresurface layers from a metallic component. An acid, base, or otherchemical etchant fluid is applied to an area of a component for a periodof time and dissolves a surface layer of the component. Various methodsmay be used to bring the etchant fluid into contact with the component.

One known method involves filling a large tank with etchant fluid andimmersing a component in the fluid. Masking material may be used toprevent the etchant fluid removing a surface layer from the entirety ofthe component. Etch tanks may have a negative environmental impact, aswell as being inefficient and costly to run. They may also produce largequantities of gas and fluid emissions. Specialist disposal of used andwaste product is required, increasing maintenance and running costs.Additional finishing operations are also often required to counteractthe effects of the etchant fluid where etching was not required, evenwhen a suitable masking material is used.

Another known method of applying etchant fluid to a component is “swabetching”, where a liquid etchant is painted on to a surface of acomponent for a given time. This often results in unsightly andinconvenient “runs” of etchant fluid straying into areas where surfaceetching was not required. Swab etching is also a comparatively labourintensive method of surface etching, involving close operator contactwith hazardous chemicals

Etchant fluids may be heated or subjected to ultraviolet stimulation toincrease etch rate. However, in combination with the above methods,these practices involve high capital cost as well as increased labourand etchant response is subject to line of sight and illumation issues

A particularly difficult problem in surface etching is the removal ofmaterial from fine surface features such as are found in laser cut,machined or welded surfaces and the interfaces between such surfaces.Weld contours, particularly in root and toe regions, presentdifficulties for the manipulation of line of sight based materialremoval processes. Welds constitute points of material micro structuralvariation and it is therefore undesirable to unduly thin a weld regionor to introduce additional stresses through machining.

SUMMARY OF INVENTION

According to the present invention, there is provided apparatus forapplying a fluid to a target area of a component, comprising a fluidapplicator and means for guiding the fluid applicator along apredetermined path with respect to the component; the fluid applicatorcomprising a body, an application head mounted on the body and operablein use to be brought into physical contact with the component, and meansfor controlling the temperature of the fluid to be applied to thecomponent.

The fluid may be any one of a chemical etchant, scale conditioner,washing fluid and/or neutralising solution. The fluid may be ofincreased viscosity and may be a paste or gel. The paste may bethixotropic.

The body may be formed from a deformable material. The body may thusaccommodate variations in surface geometry of the component such asconvex and concave regions, edge regions and re-entrant features.

The application head may comprise a brush having a brush head and aplurality of agitators which may be bristles or fins. Advantageously,the agitators of the brush act to scrub a component surface, forcingetchant fluid into fine surface features and also removing unwantedfluid from such features.

The brush head may comprise an opening, suitable to deposit or collectfluid. The apparatus may further comprise means to apply positive and/ornegative pressure at the opening. The brush head may comprise at leasttwo such openings and the apparatus may further comprise means to applypositive pressure at one opening and negative pressure at anotheropening. The openings may comprise two or more independent sections of asingle orifice, thus allowing simultaneous deposition and collection offluid.

The apparatus may comprise means for controlling the temperature of thefluid to be applied to the component. It may be desirable for the fluidto be delivered at a raised temperature or at a controlled ambienttemperature, according to the particular fluid to be applied.

The brush may be mounted for rotation about an axis that issubstantially parallel to a surface of the body on which it is mounted,a surface of the brush head from which the agitators project beingsubstantially cylindrical. In this manner, the brush may pass over thecomponent surface in a manner similar to that of a vacuum cleaner, theagitators scouring the component surface.

The plurality of agitators may project from the surface of the brushhead in a helical pattern that winds about the brush head. The pluralityof agitators may project from the surface of the brush head in at leastone chevron pattern, which may be formed about the at least one openingof the brush head.

The brush may be mounted for rotation about an axis that issubstantially normal to a surface of the body on which it is mounted, asurface of the brush head from which the agitators project beingsubstantially planar.

The brush may comprise at least two regions, the regions being operableto rotate in different directions. The regions may be concentric.

The plurality of agitators may project from the planar surface in aspiral configuration.

The length and stiffness of the agitators may vary across the brush. Thebrush may comprise regions of different length and/or stiffnessagitators.

The brush may be mounted for rotation in both clockwise andanticlockwise directions.

The agitators of the brush head may comprise bristles or they maycomprise fins.

A plurality of brushes may be mounted for rotation on the body of thefluid applicator about parallel axes.

At least two of the plurality of bushes may comprise different agitatorconfigurations.

The means for guiding may comprise a mechanical manipulation arm onwhich the fluid applicator may be operable to be mounted.

The means for guiding may comprise a track, along which the fluidapplicator may be operable to be driven. The track may be formed from adeformable material and may be assembled into a frame. The track maycomprise a racked surface/rack and pinion arrangement.

The means for guiding may further comprise means for manipulating thecomponent.

According to another aspect of the present invention, there is provideda method of applying a fluid to a target region of a component using anapparatus of the first aspect of the present invention, comprisingconnecting a fluid supply to the fluid applicator, mounting the fluidapplicator on the means for guiding the applicator along a predeterminedpath, bringing the applicator head into physical contact with the targetregion of the component, causing the applicator to be guided along thepredetermined path while depositing fluid through the applicator fromthe fluid supply, and controlling the temperature of the fluid to beapplied to the component.

The fluid may be any one of a chemical etchant scale conditioner,washing fluid and/or neutralising solution. The fluid may be ofincreased viscosity and may be a paste or gel. The paste may bethixotropic.

The means for guiding may comprise a flexible track and the method mayfurther comprise locating the flexible track about the component, suchthat the applicator traces the predetermined path along the componentwhen travelling along the track. Locating the flexible track maycomprise constructing a frame of the flexible track about the component.

The means for guiding may comprise a mechanical manipulation arm and themethod may further comprise programming the mechanical manipulation armto move the applicator such that the applicator traces the predeterminedpath along the component.

The method may further comprise mounting the component for rotation.

The means for guiding may further comprise means for manipulating thecomponent, the method may further comprise mounting the component on themeans for manipulating the component, and the various means for guidingmay cooperate to cause the applicator to be guided along thepredetermined path.

Depositing fluid through the applicator may comprise applying pressureto the fluid at a fluid opening in the application head. Depositingfluid through the applicator may also comprise causing the applicationhead to rotate.

The method may further comprise collecting fluid under a negativepressure applied at the opening in the application head.

The method may further comprise controlling the temperature of thecomponent. The method may further comprise heating and/or cooling thecomponent.

According to another aspect of the present invention, there is provideda chemical etchant comprising titanium dioxide as a thickening agent.The viscosity of the etchant may be above that of the constituentetchants and more specifically between 400-7500 cP. Viscosity enhancingmedia may also include inert oxide powders or gels.

According to another aspect of the present invention, there is providedan applicator for depositing a fluid on a component surface, comprisinga body, a brush mounted for rotation on the body, the brush comprising abrush head and a plurality of bristles and a fluid passage extendingthrough the brush head and comprising at least one opening thatcommunicates with a bristled surface of the brush head.

The fluid may comprise etchant, detergent containing wash fluid, scaleconditioner or neutralising agents.

The fluid passage may comprise two sub passages, operable to be broughtinto communication with each other.

BRIEF DESCRIPTION OF THE DRAWINGS

For a better understanding of the present invention, and to show moreclearly how it may be carried into effect, reference will now be made,by way of example, to the following drawings in which:

FIG. 1 illustrates a typical weld line in a component;

FIG. 2 illustrates a fluid applicator on a component;

FIG. 3 shows expanded sectional and side views of a fluid applicator incontact with a component;

FIG. 4 a, b and c illustrate a sample application head in the form of abrush deforming on application under variable pressure;

FIG. 5 illustrates differences in brush contact area resulting fromdeformation under variable pressure;

FIG. 6 shows a rectangular bristle configuration;

FIG. 7 shows a curved bristle configuration;

FIG. 8 shows a varying bristle configuration;

FIGS. 9 and 10 show contra-rotating or oscillating brushes;

FIG. 11 illustrates a fluid applicator and brush/bristle arrangement;

FIG. 12 illustrates an advantageous arrangement of brushes on a body ofa fluid applicator and resultant etchant flow path;

FIG. 13 is a leading end view of a fluid applicator in position over acomponent;

FIGS. 14 and 15 are end views of an example brush showing bristleconfigurations;

FIG. 16 illustrates an end and sectional view of a brush;

FIG. 17 is a side view of a fluid applicator in position on a component;

FIG. 18 shows attachment arms;

FIG. 19 illustrates an application head in the form of a rotating oroscillating brush;

FIG. 20 shows a brush arrangement on a fluid applicator;

FIG. 21 shows a bristle arrangement on a brush;

FIG. 22 illustrates a frame constructed around a component;

FIG. 23 illustrates a mechanical manipulation arm;

FIG. 24 shows a treatment arrangement for rotating a component about anaxis whilst maintaining applicator position;

FIGS. 25 a-e show a temperature control arrangement; and

FIG. 26 shows a diagrammatic view of the temperature control arrangementof FIGS. 25 a-e.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

The present invention relates to an apparatus and method for applying afluid such as a chemical etchant to a target area of a component. Thefollowing description uses the example of a weld line as a targetfeature of a component, an area of which may be appropriate for chemicaletching. FIG. 1 illustrates a typical weld line 2, such as might befound on a metallic drum assembled using electron bean welding, aroundwhich is a heat affected zone 4. If the drum is produced from titanium,an alpha case layer can occur within the heat affected zone 4. Thislayer is understood to be an oxygen enriched surface layer of titaniumthat acts to reduce the fatigue life of the component. It is thereforedesirable to remove this alpha case layer using a locally appliedchemical etchant including for example Nitric, Hydrofluoric,Hydrochloric or Hydroflourosilic acids. The etchant is applied over atarget area 8 that includes the weld line 2, the heat affected zone 4and a safety zone 6. It will be appreciated that the present inventionis suitable for use with a wide range of surface features, a weld beingused merely as a convenient example. The range of application for theinvention also includes the entire surface of an aerofoil, blink or hubincluding edge and radius/fillet features.

One aspect of the present invention involves the development of aparticularly advantageous chemical etchant for use with the apparatusand method of the invention. Known etchant combinations, such as thoseemploying Hydroflourosilic acid with Nitric acid or Hydrofluoric acidwith Nitric acid are enriched with Titanium Dioxide. TiO₂ acts as athickening agent, increasing the viscosity of the etchant to that of apaste. Water based gel and other inert oxide powders may also beemployed as a thickening agent to achieve the required viscosity, atwhich the paste will substantially adhere to a component surface, andwill not run along the surface. It is a requirement of the etchant pastethat it must remove a controlled and uniform layer of between 0.5 and15.0 μm. Certain applications may require removal of a layer of up to75.0 μm.

With reference in particular to FIGS. 2 and 3, an apparatus 5 forapplying a fluid to a target area of a component comprises a fluidapplicator 10 and means for guiding the fluid applicator along apredetermined path (partially illustrated at 12). The fluid applicator10 comprises a body 14 and two pairs 16, 18 of application heads in theform of brushes. The brushes are mounted on the body 10 for rotationabout parallel axes 20, 22, each of which extends substantially normallyto the surface 24 of the body 10 on which the brushes are mounted. Inuse, the apparatus is brought into proximity with a component 26, atarget area of which is to have etchant fluid applied. Once in position,the means for guiding the fluid applicator 10 causes the applicator toadvance towards the component (indicated at arrow 27) such that thebrushes are brought into physical contact with a surface 28 of thecomponent 26. Relative motion between the fluid applicator 10 and thecomponent 26 is brought about, as indicated by arrows 29, and the fluidapplicator 10 deposits a layer of etchant fluid 30 on the surface 28 ofthe component 26. The fluid applicator 10 will pass over the surface ofthe component 26 at least once to deposit etchant fluid 30 and at leastonce to remove etchant fluid 30. That is to say, the fluid applicator 10will make at least two passes over the surface of the component 26, atleast one of the passes being to apply etchant fluid 30, and at leastone of the passes to remove etchant fluid 30. The fluid applicator 10may also pass over the surface of the component 26 to agitate theetchant fluid 30. Further detail of the process by which etchant fluidis supplied to the fluid applicator and depositing on the surface arediscussed below.

FIG. 3 shows expanded sectional and side views of the fluid applicator10 in contact with the component 26. Each pair 16, 18 of applicatorheads comprises two brushes 32, 34, 36, 38, each of which is mounted forindependent rotation. An optional extra pair of application heads 40 isillustrated in the sectional view. Further detail of this and otherconfiguration options for the applicator heads is discussed below. Withparticular reference to the side view of FIG. 3, each brush 32, 34, 36,38 in each pair 16, 18 of brushes rotates in an opposite direction. Thusthe leading pair 16 of brushes 32, 34 rotate inward with respect to eachother and the direction of advance, from right to left across FIG. 3. Itwill be understood that each pair 16, 18 of brushes may be replaced by asingle brush, positioned along the centre line of the target area, inthis case the weld line 3. Each single brush may rotate clockwise oranticlockwise as required.

It will be appreciated that the outer extent of the target area 8 overwhich the etchant fluid is deposited is defined by the extent of thesafety zone 6. It may be desirable to vary the width of the safety zone6 during application of etchant fluid. Such variation may be achievedthrough appropriate brush selection and manipulation of the separationbetween the fluid applicator 10 and the component 26. FIG. 4 aillustrates a sample application head in the form of a brush 50, whichmay be representative of any of brushes 32, 34, 36, 38 described above.The brush 50 comprises a brush head 52 and a plurality of agitators 54.The agitators may be bristles, as illustrated, or may take the form offins. The following description refers to agitators in the form ofbristles 54, but it will be appreciated that the description couldequally be applied to agitators 54 in the form of fins. The bristles 54project from the brush head 52 to define a domed brush periphery, thefurthest extent of which is brought into contact with the surface 28 ofthe component 26 by a comparatively light force F₁. This light forceresults in a relatively small contact area A₁ between brush bristles 54and component 26 at the component surface 28. The bristles 54 of thebrush 50 are relatively flexible and may be deformed as illustrated inFIGS. 4 b and 4 c. A larger force F₂ may be applied to the brush 50,deforming the longest bristles and bringing more of the domed periphery56 into contact with the component surface 28, resulting in a largercontact area A₂. A larger force still F₃ may be applied, as illustratedin FIG. 4 c, resulting in a further increased contact area A₃. Thedifference in contact area that can be achieved is illustrated in FIG.5. The target area over which etchant fluid is applied can thus bevaried according to requirements. Deformable bristles having a domedperiphery as illustrated may also be particularly applicable for certaingeometries of feature within the target etch area. For example, certainweld geometries may be suited to longer, deformable bristles such asthose illustrated in FIG. 4 a.

FIGS. 6, 7 and 8 illustrate bristle configuration options for brush 50.The plurality of bristles 54 may define a rectangular, planar brush, asillustrated in FIG. 6, a domed brush, as illustrated in FIGS. 4 a and 7,or the bristles may define a brush having concentric annular steps, asillustrated in FIG. 8. The strength and type of bristle may also varywithin the brush head. For example and with reference to FIG. 9, thebrush 50 may comprise an inner core of short, firm bristles 56, aconcentric ring of longer, medium strength bristles 58 and an outersurrounding concentric ring of longer soft bristles capable of increaseddeformation. Such variation in bristle length and strength results in aprogressive scrubbing effect. Varying the separation between the fluidapplicator 10 (and hence brush 50) and the component surface 28 not onlyalters the deformation of the softer outer bristles but may alsodetermine the thickness of the fluid etchant layer deposited on thesurface.

Each of the example brushes 50 illustrated in FIGS. 6 to 8 is shownrotating in a regular manner in a single direction. However, a singlebrush 50 may include contra-rotating or oscillating sections, asillustrated in FIGS. 9 and 10. An inner core 56 of stiff bristles mayrotate in a different direction to an intermediate ring 58, which inturn is rotating in a different direction to the radially outer ring 60.Such contra-rotation or oscillation provides increased agitation to theetchant fluid being dispensed, improving the mixing of titanium ionsfrom the substrate into the solution and thus assisting with the surfacelayer removal process. In addition, contra-rotating or oscillatingsections help to ensure that bristles contact all the variable surfacegeometry and undulating features associated with surface finishes suchas welds. No matter what combination of rotational elements is employedfor the brushes of the fluid applicator 10, the radially outer ring ofthe final pair 18 of brushes should rotate inwards with respect to eachother and the direction of advance, as illustrated in FIG. 11, so as toensure that etchant fluid is encouraged into the weld line 2.

FIG. 12 illustrates an advantageous arrangement of brushes on a body ofa fluid applicator 10 comprising eight separate brushes. At the leadingedge 70 of the fluid applicator 10 is a first stage brush 72 rotating inan anticlockwise direction. The first stage brush 72 is a comparativelysmall brush with firm bristles, of the type illustrated in FIG. 6 or 7.This brush covers the immediate weld pool 2 and the heat affected zone 4with the firm bristles employed to scrub the zone while chemicalreaction occurs, mechanically assisting the etching process. Etchantfluid is fed through the centre of the brush 72 and the rotation of thebrush 72 feeds the etchant fluid outwards under centrifugal forces.Behind the first stage brush 72 is a pair of second stage brushes 74,76. These are larger brushes comprising firm, medium and soft bristles,as illustrated in FIGS. 8 and 9, and may include contra-rotating oroscillating sections. The second stage brushes 74, 76 scrub the heataffected zone 4 and spread etchant fluid over the area to be treated.Etchant fluid is fed through the centre of the brushes 74, 76 and therotation of the brushes 74, 76 feeds the etchant fluid outwards undercentrifugal forces. The majority of the etchant fluid is deposited alongthe central line of the target area 8 as a result of the internalrotation of the second stage brushes 74, 76. Behind the second stagebrushes 74, 76 is a third stage brush 78. The third stage brush 80 isalso a comparatively small brush with firm bristles, of the typeillustrated in FIG. 6 or 7. This brush also covers the immediate weldpool 2 and the heat affected zone 4 with the firm bristles employed toscrub the zone while chemical reaction occurs, mechanically assistingthe etching process. Etchant fluid is fed through the centre of thebrush 78 and the rotation of the brush 80 feeds the etchant fluidoutwards under centrifugal forces. Behind the third stage brush 78 is apair of fourth stage brushes 80, 82. These are larger brushes comprisingfirm, medium and soft bristles, as illustrated in FIGS. 8 and 9, and mayinclude contra-rotating sections. No etchant fluid is fed through thefourth stage brushes 80, 82, these brushes scrub and spread previouslydeposited etchant fluid over the area to be treated. At least theoutermost rings of the fourth stage brushes rotate outwards with respectto each other and the direction of advance, so as to concentratedeposition of etchant fluid away from the centre areas and even thedistribution. Finally, behind the fourth stages brushes 80, 82 is a pairof fifth stage brushes 84, 86. These are medium sized brushes of thetype illustrated in FIGS. 8 and 9, and comprise firm, medium and softbristles. No etchant fluid is fed through the fifth stage brushes 84,86. These brushes spread and agitate the previously deposited etchantfluid, concentrating it from the outer regions to the central region.The brushes do not in fact contact the surface of the component but areraised slightly, thus leaving a thin layer of etchant fluid where thebristles do not make contact (illustrated as area 90 on the Figure). Theseparation between the fifth stage brushes 84, 86 is increased withrespect to the earlier stage pairs so that the brushes extend slightlybeyond the target area 8, collecting etchant fluid that has been spreadby the fourth stage brushes 80, 82. The fifth stage brushes also act toagitate etchant fluid over the outer reaches of the target area, helpingto produce equal etchant effects over the entire area. The combinedeffect of the five stages of brushes is to leave a fully agitated thinlayer of etchant fluid over the entire target area 8, with a thickerdeposited layer in the central region of the weld 2 and heat affectedzone 4.

FIG. 13 is a leading end view of the fluid applicator 10, describedabove with reference to FIG. 12, in position over the component 26. Thecentral first stage brush 72 can be seen partially obscuring the secondstage brushes 74, 76. The variable stiffness bristles of the secondstage brushes 74, 76 deform whist rotating to scrub and adapt to thevariable surface of the component while at the same time agitating thedeposited etchant fluid to ensure thorough mixing.

Etchant fluid is deposited via the application head brushes as mentionedabove. A central opening in the brush head allows fluid etchant to bedeposited, while the rotating action of the brush encourages spread ofthe fluid over the entire contact area. Positive pressure may be appliedto fluid at the opening to encourage deposition. Once the surface of thecomponent has been etched to the required depth, it is necessary toremove the fluid and to clean the component surface. The same centralopening may be used to collect spent etchant fluid, assisted by negativepressure or a vacuum applied at the opening. Positive or negativepressure may be applied at the opening of a fluid conduit that is incommunication with the opening and also with a fluid reserve and otherexternal mechanisms. A water feed may be incorporated to assist with thecollection/cleaning of the component surface. Deposition/spreading andcollection of fluid etchant may be assisted by the bristle configurationof the brushes. FIGS. 14 and 15 are end views of an example brush 100,which may be representative of any of the fluid applicator brushesdescribed above. The brush 100 comprises bristles 102 that are arrangedto form a spiral, graduating outwards from the central opening 104.During deposition, when positive pressure is applied at the centralopening, the brush rotates in a clockwise direction, as illustrated byarrow A in FIG. 14 and FIG. 15 a. The spiral configuration of thebristles assists the natural spreading motion of the clockwise rotationand encourages even distribution of the deposited fluid. When it isnecessary to recover used etchant fluid, the brush 100 is rotated in ananti clockwise direction, as illustrated by arrow B in FIG. 14 and FIG.15 b. The anti clockwise rotation of the spiral causes the outer mostregions of the spiral to act as a scoop, collecting up the etchant fluidand conveying it into the spiral, towards the central opening wherenegative pressure is applied to suck the gathered fluid into the fluidconduit (not shown). The bristles of the brush 100 may be of variablestiffness as discussed above but in a preferred example, the spiralarrangement bristles are all of a medium stiffness and uniform length.Such an arrangement assists in maintaining the spiral configuration, andthus improves the efficiency of the distribution/collection action ofthe bristles.

It has been discussed above that agitation of the etchant fluid while onthe component surface assists with mixing and ensuring efficientmaterial removal. Agitation ensures that a layer of depleted etchantfluid and evolved gaseous product from the etching reaction does notbuild up immediately adjacent to the component surface. One desirableway of agitating and ensuring efficient surface removal is to cycleetchant fluid during the etch process. Continually depositing andcollecting fluid ensures that the fluid remains well mixed and spentfluid is not allowed to accumulate. In addition, deposited fluid may becollected and reheated or cooled before being redeposited, thus ensuringthe fluid retains optimal efficiency within predefined specificationlimits within the range 10-90° C. This also ensures that a previouslydiscussed wash stage may act to pre-heat the component to aid intemperature control of the fluid once deposited. Recycling fluid in thisway ensures that the minimum amount of fluid is used to achieve therequired depth of material removal, providing both economic andenvironmental advantages. FIG. 16 illustrates an end and sectional viewof a brush that may be employed to circulate etchant fluid, as well asdepositing and/or collecting as necessary. The brush 110 has a centralopening that is divided into two independent sections for deposition andremoval of fluid. It will be appreciated that while these sections maybe in communication with each other at some external location, to allowfor the cycling of etchant fluid, at the opening location they areindependent, to allow positive pressure to be applied at the fluidoutlet and negative pressure to be applied at the fluid inlet. Withreference to FIG. 16, fluid etchant is fed out of the brush head throughthe outlet indicated at location 1 on the Figure. Relatively firmbristles provide a path from the brush head to the component surface andcentrifugal force encourages outward spreading of the etchant fluid onceon the component surface. Radially outwards of feed location 1 is afirst clearing zone indicated at location 2. There is no fluid feed inthis area. The first clearing zone 2 receives fluid from the feedlocation 1 via centrifugal forces and relies upon such forces to spreadthe fluid as the brush rotates. The bristles in the first clearing zone2 are softer than those in the feed location 1 to allow spreading offluid and scrubbing of complex surfaces. Radially outwards of the firstclearing zone 2 is a second clearing zone 3. There is also no feed inthe second clearing zone 3, this area receives etchant from the firstclearing zone 2 via centrifugal forces and relies on these forces tospread fluid as the brush 110 rotates. The bristles in the secondclearing area 3 are slightly firmer than those in the first clearingarea, to ensure that only a controlled amount of etchant is passed intothe radially outer removal zone 4. The removal zone 4 also has no fluidfeed but receives fluid spread from the second clearing zone undercentrifugal forces. The removal zone is bounded by a thick wall of fine,firm bristles that allow fluid in removal zone 4 to be evacuated underreduced pressure that is applied via the removal section of the centralopening.

FIG. 17 is a side view of a fluid applicator 10 having a body 14 inposition on a component 26 and partially illustrating a means forguiding the fluid applicator, indicated at 12. The body 14, on whichapplication heads in the form of brushes are mounted, is made of adeformable material, for example a polymeric material and may be ofdifferent sizes or shapes depending on the component and/or the geometryof the area to be treated. The deformable material allows the body toadapt to different component surface geometries. The means for guidingthe fluid applicator 10 may have several attachment arms 120, 122, 124by which it is connected to the body 14 of the fluid applicator 10. Eachof these attachment arms may be independently moveable or extendable tomanipulate the body 14 of the fluid applicator 10 such that theapplication heads are maintained in precisely the desired spatialrelationship with the component surface, no matter what the componentsurface geometry may be. For example, if the component surface has adistinct concave curve, the outer attachment arms 120, 124 may beretracted, forcing the body to deform into a convex shape to match thesurface of the component. Any other surface geometry may be similarlyaccommodated by appropriate manipulation of the deformable body,ensuring that the application heads are maintained in physical contactwith the component surface to deposit, agitate and collect fluid etchantas required.

Further detail of the attachment arms and means for guiding 12 isillustrated in FIG. 18, where it can be seen that each of the attachmentarms may be independently extended, retracted and rotated or pivoted tomanipulate the body 14 in the position and shape required. In addition,the post 126 on which the attachment arms are supported may also rotate,and the attachment arms may be translated along the post. Further detailof the different embodiments of the means for guiding the fluidapplicator 10 is discussed below with respect to FIGS. 22 to 24.

FIGS. 19 to 21 illustrate an alternative embodiment of application headin the form of a brush 200. The brush 200 is mounted in a fluidapplicator 10 as described above. The brush 200 is designed to bemounted for rotation about an axis that runs substantially parallel to amounting surface of the body 14 of the fluid applicator, substantiallyin the manner of a vacuum cleaner. The brush 200 comprises a brush head202 having a substantially cylindrical outer surface on which in mounteda plurality of bristles 204. In one embodiment, illustrated in FIG. 19,the plurality of bristles 204 is arranged to form a helix, winding aboutthe brush head 202. A plurality of openings 206 open onto the bristledsurface of the brush head 202. These openings 206 perform the samefunction as the central openings discussed above with respect to thefirst described embodiment of application head. The openings 206 permitdeposition and collection of etchant fluid that may be provided to (asindicated at arrow 208) and/or removed from (as indicated at arrow 210)the brush 200.

FIG. 20 illustrates how several of the brushes 200 may be mounted forrotation on a body 14 of a fluid applicator 10. Alternating helicalbristle configurations ensure even spread and distribution of adeposited layer of etchant fluid over the target area 8 of the component26. During deposition, some or all of the openings may deposit fluid.Any bristles located adjacent an opening that is not depositing fluidassist the process by agitating already deposited fluid. During removal,all or some of the bristles may be cause to rotate in the oppositedirection, channeling spent fluid towards the openings that receivefluid under negative pressure. The arrangement of the plurality ofbristles 204 may be altered to specifically assist with fluid depositionand removal. FIG. 21 illustrates an alternative arrangement in which theplurality of bristles 204 are arranged in a series of chevrons, eachchevron centred upon an opening in the brush head surface. Duringdeposition, indicated by arrow A and the left hand part of FIG. 21, thebrush head rotates such that the chevrons of bristles act to spread thedeposited fluid across the surface of the component, as indicated byarrow B. During collection, as indicated by arrow C and the right handpart of FIG. 21, the brush head rotates such that the chevrons ofbristles act to scoop up etchant fluid and direct it into the path ofthe openings that can collect the fluid under the application ofnegative pressure, as illustrated by arrows D.

A first embodiment of the means for guiding the fluid applicator 10 isillustrated in FIG. 22. According to this embodiment, the means forguiding comprises a flexible track 300 that is assembled into a frame310 around the component 26 to be etched. The track 300 may be flexibleor may be of rigid material and construction. The track 300 is assembledinto the frame 310 by a series of clamps 302 that secure the track inplace and prevent movement. Pads 304 may be employed to prevent theclamps 302 and/or track 300 coming into contact with the component 26and perhaps damaging the component surface. The track 300 carries a rackor other means by which the fluid applicator may be secured on and movedalong the track 300 in the desired direction. The fluid applicator 10 ismounted on the track such that the application heads can contact thecomponent surface over the target area to deliver, agitate and finallycollect etchant fluid. A single track may support multiple heads toreduce treatment time. The precise location of the track may bedetermined using for example the CAD drawings of the component. Thetarget area to be treated, for example a weld on an aerofoil component,can be precisely identified on the drawings or CAD software. A path forthe fluid applicator that will result in treatment of the target areamay then be determined. The appropriate location for the track may thenbe calculated from the predetermined path and the known geometry of thefluid applicator 10 and the track location may be fixed and the frameconstructed.

FIG. 23 illustrates another embodiment of the means for guiding thefluid applicator along a predetermined path. According to thisembodiment, the means for guiding is a computer controlled mechanicalmanipulation arm 400. The mechanical manipulation arm is preferably amulti axis arm that allows fine control and manipulation of the locationand orientation of the fluid applicator. The spatial coordinates of thetarget area 8 may be provided to the control unit which determines apath along which the fluid applicator must travel in order to treat thetarget area and causes the manipulation arm to position and move thefluid applicator accordingly. A simpler manipulation arm may be employedin combination with manipulation of the component to be treated, asillustrated in FIG. 24. The component, for example a drum may be mountedfor rotation on a platform about a fixed axis, reducing the amount oftranslation required of the means for guiding the fluid applicator inorder to enable the fluid applicator to contact any point on the surfaceof the component 26. For example the fluid applicator may trace a spiralover the component, or may trace a series of discrete circles using anoscillatory pattern, or set concentric path.

The use of CAD software to determine a predetermined path for the fluidapplicator to follow, and then to instruct a manipulation arm or directthe construction of a frame allows a high degree of accuracy to beachieved while minimising operator contact with etchant media. In eachcase, the predetermined path may involve several discrete sections, overwhich the fluid applicator may need to pass but which should not haveetchant media applied. The flow of etchant fluid to the fluid applicatormay be stopped as the fluid applicator passes over such regions. Inaddition, or in the alternative, the fluid applicator may be offset fromthe component surface as it passes over such sections.

It will be appreciated that it may be desirable to vary the offset ofthe fluid applicator from the component surface during treatment so asto vary the thickness of the deposited layer of etchant fluid. Forexample, the fluid applicator may be in close physical contact with thecomponent surface during deposition, slightly further away duringmanipulation/agitation of the etchant fluid so as to merely mix theetchant rather than remove if from the surface, and then in closecontact again for etchant removal. The actual process cycle may be morecomplicated than has so far been described. For example, a full processcycle may include the following steps:

-   -   i) Wash—a first pass of the target area is conducted to        thoroughly scrub the target area    -   ii) Scale condition—a viscous scale conditioner is applied using        the fluid applicator 10 to prepare the surface    -   iii) Wash—a third pass is conducted to remove the scale        conditioner and clear the surface    -   iv) Etch—a layer of etchant fluid is applied as described above    -   v) Agitate—several passes may be made cycling and agitating the        etchant paste to ensure even and thorough removal of the        required thickness of surface layer    -   vi) Wash—a penultimate pass is made to remove the etchant and        clear the surface    -   vii) Dry and Clean—a final pass is made to scrub the surface and        remove any last loose material an air-knife approach may be        used.

It will be appreciated that the bristle requirements for the differentprocess stages may be different. For example firmer bristles arerequired for depositing layers of fluid while longer, softer bristlesmay be preferred for agitation and cleaning. The various requirementsmay be accommodated in a single applicator by employing severaldifferent brushes on a single applicator and by employing variablebristle types on individual brush heads, as described above. It may alsobe desirable to employ specific brushes within the applicator forspecific tasks. For example it may be desirable to use different brushesfor the application and removal of the scale conditioner to thoseemployed for application, agitation and removal of the etchant fluid.Different brushes, tailored to the specific process stage requirements,can be mounted on a carousel and moved between operating and holdingpositions as required. A water feed may be incorporated to assist withthe wash process stages as required.

It will be understood that variations can be made to the specificembodiments of apparatus described above without departing from thescope of appended claims. For example, additional agitation ortemperature control may be provided by steam or gas jets deliveredeither from the applicator body or through the application heads of thefluid applicator. Additional agitators may also be provided in the formof flutes, ribs or supplementary bristles. Such agitators may be mountedon the application heads or may be mounted on separately on the body.Heating or cooling may be provided via the circulatory control unit,body or application heads to increase or decrease the temperature of thescale conditioning, wash or etchant fluid. It will be understood thatheating etchant fluid may increase the rate at which surface material isremoved, although this may result in an increased health and safetyconcern. Depth probes and/or a surface scanner/analyser may also beincorporated into the fluid applicator, with the potential forincorporation of electrolytic fluid monitoring and control.

The temperature of the component may be controlled. The temperature ofthe component may be controlled by cooling and/or heating the componentdirectly or by cooling and/or heating the atmosphere in which thecomponent is held throughout the process. FIG. 25 a-e and FIG. 26present a means for temperature control of the component 26, comprisingan enclosure 500 for housing the component 26 during the method of thepresent invention. A door/shutter 510 is lifted from a rest position(FIG. 25 a) by an actuation means 520 and the component 26 is movedinside the enclosure 500 (FIG. 25 b). The actuation means 520 thenlowers the door/shutter 510 such that the component 26 is containedwithin the enclosure 500 (FIG. 25 c). Once inside the enclosure 500, themethod of the present invention is worked, with the temperature of theatmosphere inside the enclosure and the temperature of the component 26being monitored and controlled to within predetermined and desirablelimits. Once the method of the present invention is complete, thedoor/shutter 510 is lifted from the closed rest position (FIG. 25 d) bythe actuation means 520 and the component 26 is moved outside of theenclosure 500 (FIG. 25 e). A micro switch fitted to the door/shutter 510is operable to monitor the position of the door/shutter 510 and thusprevent deployment of the application head 10 and chemicals while thedoor/shutter 510 is open.

FIG. 26 shows the component 26 when located within the enclosure 500during the method of the present invention. Thermocouples 530 arearranged around the enclosure to measure the temperature of theatmosphere within the enclosure 500. Additional thermocouples 532 areattached to multiple locations on the surface of the component 26 tothereby measure the temperature of the component 26. Thermocouples 534are also attached to an output duct of an atmospheric heater/cooler 536.Thermocouples 538, 540 are additionally attached to the input and outputrespectively of a heater/cooler chemical reservoir 542 used to containthe chemicals used in the method of the present invention. Thethermocouples 530, 532, 534, 538, 540 are input to the heater/flowcontrol unit 544. In dependence upon the input from the thermocouples530, the heater/flow control 544 unit makes adjustments to theatmospheric heater 536 to maintain the atmospheric temperature to withina desired temperature range. In dependence upon the input fromthermocouples 532, 534, 538 and 540 the heater/flow control unit 544makes adjustments to the heater/cooler chemical reservoir 542 tomaintain the temperature of the chemicals being applied to the component26 via the application device 10 to within a desired temperature range.Following application via the application device 10, a fluid flowcontrol device 546 recirculates the fluid into the heater/coolerchemical reservoir 542 or channels the fluid into a series of fluidspecific reservoirs 548. From the fluid specific reservoirs 548, fluidsmay then be pumped into heater/cooler chemical reservoir 542 via thefluid flow control device 546 and then recirculated and reheated asrequired. Alternatively fluids may be channeled from the fluid specificreservoirs 548 into waste disposal tanks 560. Following conclusion ofthe chemical process, a wash fluid shall cleanse and neutralise thesystem, with fluid passing directly through the fluid flow controldevice 546 and fluid specific reservoirs 548 into the waste disposaltanks 560.

The component may be maintained at a temperature of about 293K by thetemperature control means for scale conditioning part of the process.The component may be maintained at about 363K by the temperature controlmeans for the cleaning and etching parts of the process.

It will be further understood that while various aspects of the presentinvention have been described in combination, such combinations are notintended to be limiting in scope. Any aspect of the present inventionmay be employed in combination with any other aspect of the presentinvention above described.

The present invention has been described with particular reference tothe surface processing of a weld line. However, the present invention isapplicable to any circumstance in which surface treatment of a targetarea of a component is required. The maneuverability and versatility ofthe apparatus of the present invention renders it particularly suited tothe treatment of curved components such as aerofoils for gas turbineengines. The adaptability and fine control provided by the apparatus ofthe present invention enables accurate treatment of convex and concavesurface areas including edge and tip surfaces and re-entrant featuressuch as weld crowns and underbeads. It will be appreciated, however,that the apparatus of the present invention can be employed for thetreatment of any kind of component. Such treatment is not limited to theparticular application of etchant fluid described, but may also includenon destructive testing applications and cleaning as well as surfacepreparation, diffusion bonding and chemical milling. The apparatus issuitable for use with metallic as well as glass and other materialcomponents.

It will be appreciated that the present invention provides an efficientand environmentally sound apparatus and method for applying an etchantor other fluid to a component surface. Fine control is provided toenable exact distribution of fluid and hence accurate surface materialremoval by etchant media. The apparatus is extremely versatile andadaptable to a wide range of component shapes and sizes. Accuratetreatment of target surface areas by the apparatus retains componentthickness and reduces chemical usage. The apparatus is self contained,not requiring the use of sealant or masking material. The invention alsocontains scope for miniaturisation, use on bimetallic components orassemblies and use on assemblies containing non-metallics such as seals,foams, rubbers and hard polymers.

To avoid unnecessary duplication of effort and repetition in the text,certain features are described in relation to only one or severalaspects or embodiments of the invention. However, it is to be understoodthat, where it is technically possible, features described in relationto any aspect or embodiment of the invention may also be used with anyother aspect or embodiment of the invention.

1. Apparatus for applying a fluid to a target area of a component,comprising a fluid applicator; and means for guiding the fluidapplicator along a predetermined path with respect to the component; thefluid applicator comprising: a body; an application head mounted on thebody and operable in use to be brought into physical contact with thecomponent; and means for controlling the temperature of the fluid to beapplied to the component.
 2. Apparatus as claimed in claim 1, whereinthe application head comprises a brush having a brush head and aplurality of agitators.
 3. Apparatus as claimed in claim 2, wherein thebrush is mounted for rotation about an axis that is substantiallyparallel to a surface of the body on which it is mounted, a surface ofthe brush head from which the agitators project being substantiallycylindrical.
 4. Apparatus as claimed in claim 3, wherein the pluralityof agitators projects from the surface of the brush head in a helicalpattern that winds about the brush head.
 5. Apparatus as claimed inclaim 3, wherein the plurality of agitators projects from the surface ofthe brush head in at least one chevron pattern.
 6. Apparatus as claimedin claim 2, wherein the brush is mounted for rotation about an axis thatis substantially normal to a surface of the body on which it is mounted,a surface of the brush head from which the agitators project beingsubstantially planar and the plurality of agitators projects from thesurface of the brush head in a spiral configuration.
 7. An applicator asclaimed in claim 2, wherein the agitators comprise fins.
 8. Apparatus asclaimed in claim 1, wherein the application head comprises an openingand the apparatus further comprises means to apply positive and/ornegative pressure at the opening.
 9. Apparatus as claimed in claim 8,wherein the application head comprises at least two such openings andthe apparatus further comprises means to apply positive pressure at oneopening and negative pressure at another opening.
 10. Apparatus asclaimed in claim 2, comprising a plurality of brushes mounted forrotation on the body of the fluid applicator about parallel axes.
 11. Anapplicator as claimed in claim 10, wherein at least two of the pluralityof brushes comprise different agitator configurations.
 12. A method ofapplying a fluid to a target region of a component using an apparatus asclaimed in claim 1, comprising: connecting a fluid supply to the fluidapplicator; mounting the fluid applicator on the means for guiding theapplicator along a predetermined path; bringing the applicator head intophysical contact with the target region of the component, causing theapplicator to be guided along the predetermined path while depositingfluid through the applicator from the fluid supply, and controlling thetemperature of the fluid to be applied to the component.
 13. A method asclaimed in claim 12, wherein depositing fluid through the applicatorcomprises applying pressure to the fluid at a fluid opening in theapplication head.
 14. A method as claimed in claim 13, whereindepositing fluid through the applicator further comprises causing theapplication head of the applicator to rotate.
 15. A method as claimed inclaim 13, the method further comprising collecting fluid under anegative pressure applied at the opening in the application head.